Description

There are only two differences between this function and
ingres_connect(): First, when connecting, the
function will initially try to find a (persistent) link that is
already opened with the same parameters. If one is found, an
identifier for it will be returned instead of opening a new
connection. Second, the connection to the Ingres server will not
be closed when the execution of the script ends. Instead, the
link will remain open for future use
(ingres_close() will not close links
established by ingres_pconnect()). This type
of link is therefore called "persistent".